This invention relates to the preparation of ruthenium films using chemical vapor deposition and liquid ruthenium precursors.
Films of metals, particularly ruthenium films, are becoming important for a variety of electronic and electrochemical applications. For example, ruthenium films are generally unreactive to silicon and metal oxides, and are good conductors. Films of ruthenium have suitable properties for a variety of uses in integrated circuits. For example, they can be used in integrated circuits for electrical contacts. They are particularly suitable for use as barrier layers between the dielectric material and the silicon substrate in memory devices, such as ferroelectric memories. Furthermore, they may even be suitable as the plate (i.e., electrode) itself in capacitors.
There are a wide variety of ruthenium compounds that can be used as precursors for the preparation of such films. Many are particularly well suited for use in chemical vapor deposition techniques. See, for example, U.S. Pat. No. 5,372,849 (McCormick et al.), which discloses the use of ruthenium compounds containing carbonyl ligands and other ligands. However, such compounds typically form dimers, which are less volatile and not as easily used in chemical vapor deposition techniques. Thus, there is a continuing need for methods for the preparation of ruthenium films using chemical vapor deposition techniques.
The present invention provides methods for the preparation of ruthenium metal films. In one embodiment, the method includes the steps of: providing a liquid precursor composition comprising one or more compounds of the formula (Formula I):
(diene)Ru(CO)3
wherein: xe2x80x9cdienexe2x80x9d refers to linear, branched, or cyclic dienes, bicyclic dienes, tricyclic dienes, fluorinated derivatives thereof, derivatives thereof additionally containing heteroatoms such as halide, Si, S, Se, P, As, N, or O, or combinations thereof; vaporizing the liquid precursor composition to form vaporized precursor composition; and directing the vaporized precursor composition in combination with one or more oxidizing gases toward the semiconductor substrate or substrate assembly to form a ruthenium metal film on a surface of the semiconductor substrate or substrate assembly. Preferably, the oxidizing gas is less oxidizing than oxygen (O2). This method is particularly useful on complex structures, such as those containing one or more small high aspect ratio features (e.g., openings or post-type structures), which typically require excellent step coverage.
Complexes of Formula I suitable for use in the methods of the present invention are neutral complexes and are liquids at a temperature within a range of about 20xc2x0 C. to about 50xc2x0 C. They can be used in flash vaporization, bubbling, microdroplet formation techniques, etc., as neat liquids or in combination with an organic solvent. As used herein, xe2x80x9cliquidxe2x80x9d refers to a neat liquid (a liquid at room temperature or a solid at room temperature that melts at an elevated temperature up to about 50xc2x0 C.), or a liquid or solid in a suitable organic solvent. Suitable organic solvents that could be used include hydrocarbons such as hexane, pentane, and toluene, for example.
Methods of the present invention are particularly well suited for forming films on a surface of a semiconductor substrate or substrate assembly, such as a silicon wafer, having high surface area topology, such as high aspect ratio openings formed therein, but such gaps are not required, used in forming integrated circuits. It is to be understood that methods of the present invention are not limited to deposition on silicon wafers; rather, other types of wafers (e.g., gallium arsenide wafer, etc.) can be used as well. Also, the methods of the present invention can be used in silicon-on-insulator technology. Furthermore, substrates other than semiconductor substrates or substrate assemblies can be used in methods of the present invention. These include, for example, fibers, wires, etc. If the substrate is a semiconductor substrate or substrate assembly, the films can be formed directly on the lowest semiconductor surface of the substrate, or they can be formed on any of a variety of the layers (i.e., surfaces) as in a patterned wafer, for example. Thus, the term xe2x80x9csemiconductor substratexe2x80x9d refers to the base semiconductor layer, e.g., the lowest layer of silicon material in a wafer or a silicon layer deposited on another material such as silicon on sapphire. The term xe2x80x9csemiconductor substrate assemblyxe2x80x9d refers to the semiconductor substrate having one or more layers or structures formed thereon.
In one embodiment of the invention, a method of manufacturing a semiconductor structure, preferably having a surface with one or more small high aspect ratio features therein is provided. The method includes the steps of:
providing a semiconductor substrate or substrate assembly, which is exposed to a heater preferably set at a temperature of about 150xc2x0 C. to about 350xc2x0 C. (more preferably, at a temperature of about 200xc2x0 C. to about 250xc2x0 C.), and contained within a reaction chamber preferably having a pressure of about 10xe2x88x923 torr to about 1 atmosphere (more preferably, having a pressure of about 0.1 torr to about 10 torr);
providing a liquid precursor composition preferably at a temperature of about 20xc2x0 C. to about 50xc2x0 C., the precursor composition comprising one or more compounds of Formula I; vaporizing the liquid precursor composition to form vaporized precursor composition; and directing the vaporized precursor composition in combination with one or more oxidizing gases toward the semiconductor substrate or substrate assembly to form a ruthenium metal film on the surface of the semiconductor substrate or substrate assembly having the one or more small high aspect ratio features. Preferably, the oxidizing gas is less oxidizing than oxygen (O2).